1. Field of the Invention
This invention relates to an exposure method in a lithography technique used for semiconductor manufacturing, in particular, an immersion lithography method in which exposure is performed in a state where liquid is interposed between lens of an exposure apparatus and a substrate to be processed.
2. Description of the Related Art
In recent years, immersion lithography has received much attention. Immersion lithography is a method in which exposure is performed by filling liquid into a space between a surface of a resist film and a lens of an exposure apparatus when the resist film is subjected to exposure. To perform this method, there is proposed an immersion lithography apparatus (Jpn. Pat. Appln. KOKAI Pub. No. 10-303114), wherein the whole substrate to be processed is submerged in water in a stage to which water is supplied, and exposure is performed while the stage is moved. However, in the apparatus, since liquid is supplied to the whole stage, there is the problem that liquid is disturbed or spilled from the stage when the stage is moved at high speed. Therefore, the apparatus has the problem that the stage cannot be driven at high speed.
As a countermeasure against disturbance of liquid due to movement of the stage, there is disclosed a method of driving the stage while liquid is locally supplied to a part which is subjected to exposure (Jpn. Pat. Appln. KOKAI Pub. No. 2005-109426). In this method, to move the liquid film, which is locally interposed between the surface of the film and the lens, at high speed for immersion lithography, the surface of the resist is rendered water-repellant, or a water-repellant film is provided on the surface of the resist. This enables the stage to relatively move at high speed with respect to the optical system.
However, the immersion lithography of this type has the following problem. Specifically, there is the problem that defects occur in a resist pattern due to remaining liquid drips and localized air bubbles in immersion lithography. Further, these defects tend to occur in portions close to an edge of the substrate to be processed.
As described above, immersion lithography, in which exposure is performed while the immersed region is moved on the resist film, has the problem that defects occur in a resist pattern due to remaining liquid droplets and localized air bubbles in immersion lithography, and cause deterioration in accuracy of pattern dimensions.